I had an alchemist PC and at one point he visited the Gongfarmer (who was a half-orc employing goblins to scrape the piles)Important information to know to properly roleplay your Level 0 gongfarmer.
The use of urine for various things was unsurprising. Not that I knew about it, but there aren't a lot of sources of organic chemicals in the pre-petroleum world. We still use urea to treat diesel emissions, though we make it out of petroleum instead of piss now.
Not just medieval world, back in the 50’s and 60’s it was still being used for stain removal and as a mild disinfectant for wounds.Urine had all sorts of uses in the ancient/medieval world.
Tanners also had a reputation for stench.